I have been using them for about 2 years now and they have excellent customer service. For example, despite being a discount pre-order company they have always been willing to add reorders onto orders for me at the normal discounts for books I missed. They ship fast and generally respond to emails Wednesday-Friday.

I started using DCBS in December, but I won't be able to really give a whole lot of opinion on it until I get my first order. The 35% discount on most things help, but the shipping fee counteracts that unless you order a lot. I might try out HeavyInk, since 20% off plus free shipping might let me save more money.